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MPI_Comm_create.3.rst

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MPI_Comm_create

:ref:`MPI_Comm_create` |mdash| Creates a new communicator.

SYNTAX

C Syntax

#include <mpi.h>

int MPI_Comm_create(MPI_Comm comm, MPI_Group group, MPI_Comm *newcomm)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'

MPI_COMM_CREATE(COMM, GROUP, NEWCOMM, IERROR)
    INTEGER COMM, GROUP, NEWCOMM, IERROR

Fortran 2008 Syntax

USE mpi_f08

MPI_Comm_create(comm, group, newcomm, ierror)
    TYPE(MPI_Comm), INTENT(IN) :: comm
    TYPE(MPI_Group), INTENT(IN) :: group
    TYPE(MPI_Comm), INTENT(OUT) :: newcomm
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETER

  • comm : Communicator (handle).
  • group : Group, which is a subset of the group of comm (handle).

OUTPUT PARAMETERS

  • newcomm : New communicator (handle).
  • ierror : Fortran only: Error status (integer).

DESCRIPTION

This function creates a new communicator newcomm with communication group defined by group and a new context. The function sets newcomm to a new communicator that spans all the processes that are in the group. It sets newcomm to MPI_COMM_NULL for processes that are not in the group. Each process must call with a group argument that is a subgroup of the group associated with comm; this could be MPI_GROUP_EMPTY. The processes may specify different values for the group argument. If a process calls with a non-empty group, then all processes in that group must call the function with the same group as argument, that is: the same processes in the same order. Otherwise the call is erroneous.

NOTES

:ref:`MPI_Comm_create` provides a means of making a subset of processes for the purpose of separate MIMD computation, with separate communication space. newcomm, which is created by :ref:`MPI_Comm_create`, can be used in subsequent calls to :ref:`MPI_Comm_create` (or other communicator constructors) to further subdivide a computation into parallel sub-computations. A more general service is provided by :ref:`MPI_Comm_split`.

ERRORS

.. seealso::
   * :ref:`MPI_Comm_split`